【作者】 邓军；

【导师】 杨永全；

【作者基本信息】 四川大学 ， 水力学及河流动力学， 2002， 博士

【摘要】 在总结前人研究成果的基础上，试验研究了掺气对基岩冲刷破坏的影响；基岩冲刷过程中冲坑底部脉动压强随冲坑深度的增加而变化的特性；掺气对冲坑未形成前河床底部及基岩冲刷坑底部脉动压强的影响；掺气对射流轴线流速变化的影响等。分析了掺气对基岩冲刷影响的原因并对基岩冲刷进行了紊流数值模拟，主要成果如下： 1．试验研究了基岩冲坑底部的脉动压强，获得了基岩冲刷过程中以及冲坑稳定后，射流冲击区的脉动压强特性。表明在基岩冲刷过程中以及冲坑稳定后，射流冲击区的脉动压强与冲坑形成前一样，都是以低频大振幅为主，说明在冲刷坑形成后，射流冲击区水流与无冲坑时一样，都是大尺度涡不断破碎和小尺度涡不断生成的过程。 2．试验研究了掺气对冲坑未形成前河床底部脉动压强的影响，试验结果表明：掺气将明显增大冲坑未形成前河床底部射流冲击区的脉动压强，但掺不掺气情况下，射流滞点时均压强无量纲分布、底部无量纲时均压强沿程分布和最大脉动压强无量纲分布都遵从相同的规律。 3．试验研究了掺气对冲坑底部脉动压强的影响，结果表明：无论冲坑深度为多大，坑底脉动压强均方根值沿程分布与不掺气时相比，没有确定性的规律，射流掺气后，冲坑底部的脉动压强有时增加，有时反而减小。证明了冲刷坑的形成对下游水流流态及坑底脉动压强特性有较大的影响。 4．试验研究了掺气对基岩冲刷的影响，结果表明：掺气对射流冲刷的影响非常显著，而且掺气总是使冲坑减小。掺气浓度C_σ对冲坑深度的影响，可表达为掺气浓度与冲坑无量纲深度的幂函数关系。掺气对冲坑形态并没有实质性的影响，冲坑的宽深比随冲坑深度的减小而增大，无论造成冲坑深度减小的原因 四）1大学I学博士学位论文是掺气、降低流速还是减小入射水舌厚度，其变化规律都可用相同的直线关系表示。 5．从浮射流角度出发，推导出了求解掺气射流的方程组，并出此对掺气射流的速度衰减进行了分析；试验研究了射流掺气与不掺气情况下，流速沿程衰减情况，结果表明：掺气浓度越大，射流速度衰减得越快，证明了掺气影响基岩冲刷的主要原因是加大了射流速度的衰减。 6．对基岩的冲刷进行了数值模拟，选取临近底部的结点处的压强（压力水头值）与结点处水深的差值，再与结点处垂直于底面方向的速度分量的0．9倍（转化为等效水头讨加作为控制参数。计算结果表明，通过恰当地选取控制参数，用数学模型来模拟基岩的冲刷是可行的；掺气与不掺气时基岩冲刷结果的计算值与实验值符合很好，结果令人满意。更多还原

【Abstract】 The existing results about scour hole was summarized. Experiments was made about the influence of aeration on scour,the dynamic pressure on the original riverbed and the scouring hole bottom,and the influence of aeration on the dynamic pressure and the velocity of submerged jet. Scour was simulated by numerical model. The main contents and conclusions are as follows:1. The dynamic pressure on the original riverbed and the scour hole are measured. The results show that the characteristics of dynamic pressure in the scour hole are the same as that on the original riverbed.2. Experiments about the influence of aeration on the dynamic pressure on the original riverbed show,aeration will obviously increase the fluctuating pressure on the original riverbed.3. Experiments about the influence of aeration on the dynamic pressure on the bottom of scour hole show,the influence of aeration on the dynamic pressure on the bottom of scour hole is ruleless.4. Experiments about the influence of aeration on scour hole show,aeration decrease the scour depth. The relationship between the air concentration and the scour depth can be expressed as an exponential function. Aeration does not affect the shape of scour hole. The ratio of the length to the depth of scour hole decreases with the increasing scour depth,in spite of the reason is the increase of the air concentration,the decrease of the jet velocity or the decrease of the jet thickness.5. Governing equations of the aerated jet flow are established. Experimentsabout the influence of aeration on the velocity of the submerged jet was made. It has been proved that the main reason of the influence of aeration on scour is the more rapid decrease of the velocity of the submerged velocity.6. A set of mathematical model was developed and the scouring was simulated. The calculated results accords with the experimental data very well.更多还原